package org.skiplist2;



import java.util.Collection;

public abstract class AbstractSkipList<E> {

    public abstract int size();

    public abstract boolean isEmpty();

    public abstract boolean contains(E e);

    public abstract boolean add(E e);

    public abstract boolean remove(E e);

    public abstract void clear();

    public abstract boolean addAll(Collection<? extends E> c);

    public abstract E first();

    public abstract E last();

}
